yesterday when I was preparing equipment for the gig and formatted all the cards, one of them gave me error (card not formatted), and I couldn't format it either. The card was working fine just two weeks earlier. I have two 5Dm2 bodies, on the same firmware, so I plugged that card to the other body, and NO error, no issues, reads the images saved on it, formatted the card without an issue. But even after formatting it won't work in the first body.